Metal-phenolic network modified melamine-formaldehyde phase-change microcapsules for solar photothermal conversion and latent heat storage

Photothermal phase-change materials couple solar-to-thermal conversion with latent-heat storage, offering a promising route to address the challenge of solar-energy intermittency and unpredictability. However, the actual development remains constrained by complex fabrication, high cost, unsatisfactory energy storage density and insufficient cycling stability. Here, a tannic acid (TA)-Fe 3+ metal-phenolic network (MPN) was constructed on melamine-formaldehyde (MF) phase-change microcapsules (MFPCMs) through a mild surface-coordination strategy, yielding MFPCM@TA-Fe. Firstly, morphological and spectroscopic characterizations supported the formation of an MPN layer while confirming that the original microcapsule structure was retained. Furthermore, molecular dynamics simulations elucidated the adsorption of TA onto the MF shell and the associated intermolecular interactions, providing molecular-level insight into the interfacial assembly process. MPN modification enhanced light absorption across 200-1200 nm while preserving high thermal-storage capacity, with melting and crystallization enthalpies of 198.9 J g −1 and 196.3 J g −1 , respectively. Under 100 mW cm −2 irradiation, MFPCM@TA-Fe reached 57.5°C and maintained a reproducible photothermal response over on/off irradiation cycles. In short, by leveraging the favorable interfacial affinity between TA and the MF shell, this work establishes a rapid and straightforward route to MPN modification, integrating photothermal conversion with latent-heat storage.